Rock drill



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IL Rm UD c@ CLN J Orlglnal Flled Dec 4 1940 /V/V/V/ Ressued Aug. 29,1944 ROCK DRILL John C. Curtis, Claremont, N. H., assignor to SullivanMachinery Company, a corporation of Massachusetts Original No.2,337,031, dated December 21, 1943,

Serial No. 368,508, December 4, 1940. Application for reissue January21, 1944, Serial No.

24 claims. (c1. 27s-19.35

This is an application for reissue cf Letters Patent No 2,337,031,granted December 2l, 1943.

This invention relates to rock drills, and more particularly toimprovements in the drill steel chuck mechanism for such drills.

It is customary to provide in a chuck mechanism for supporting andlocking a drill steel in a rock drill of the hammer type, an opening atthe forward end of the chuck through which the shank of a drill steelwith lugs formed upon its sides may be inserted when the drill steel isturned to a certain position. Within the chuck are provided longitudinalgrooves for receiving the lugs, and the grooves are of such angularextent throughout their lengths that the drill steel may be partiallyrotated when the lugs are in any of their positions between the ends ofthe grooves, to bring the lugs out of registry with the opening and intoengagement with suitable abutments. With this arrangement, it ispossible for the drill steel to turn appreciably within the chuck duringoperation of the drill, and it may at any time, except when driven by`the chuck, turn into a position bringing the lugs into alinement withthe opening. Rotary movement of the drill steel and its lugs within thegrooves during operation of the drill causes considerable wear betwenthe lugs and the parts of the chuck mechanism, and if the lugsy aremoved into positions in alinement with the opening at the forward end ofthe chuck the drill steel may be inadvertently released. By providing arecess within which the lugs may be turned by partially rotating thedrill steel when it is in only a certain position in the chuck, andp-roviding grooves 'within which the lugs are received when the drillsteel is in its normal position during operation of the drill, and whichprevent rotation of the drill steel, there is obtained a reduced wearand a locking of the drill that prevents its release.

It is an object of this invention to provide an improved rock drillchuck mechanism. It is another object of this invention to provide animproved chuck mechanism having means for holding the drill steel in alocked position during operation of the drill. It is still anotherobject to provide in an improved chuck mechanism means for reducing therelative movement between the drill steel and' parts of the chuckmechanism, thereby reducing the wear during operation of the drill.Still another object is to provide an improved drill steel chuckmechanism having improved means for supporting and driving the drillsteel and for locking the drill steel within the chuck. These and otherobjects of the invention will, however, hereinafter more fully appear.

In the accompanying drawing there is shown for purposes of illustrationone form which the invention may assume in practice.

In the drawing- Fig. 1 is a longitudinal section, taken on line I-I ofFig. 2, through the forward portion of a rock drill within which theillustrative form of the improved chuck mechanism is embodied.

Fig. 2 is a cross sectional view taken on line 2-2 of Fig. 1.

Fig. 3 is a cross sectional View taken on line 3-3 of Fig. 1.

Fig..4 is a cross sectional view taken on line 4-4 of Fig. 1.

Fig. 5 is a perspective View showing the chuck sleeve, the drivingbushing and the retaining ring of the improved chuck mechanism, theparts being shown in positions for assembly.

Fig. 6 is a detail sectional View taken on the line 6 6 of Fig. 3.

In the illustrative embodiment of the invention the improved chuckmechanism is embodied in a hammer-type rock drill comprising a cylinderI containing a reciprocable hammer piston having a striking bar 2slidably guided in a front cylinder head 3, and this striking bar isadapted to deliver impact blows to the shank 5 of a drill steel 6. As isusual in rock drills, the hammer piston is rotated as it isreciprocated, andthis rotative piston movement is transmitted to thedrill steel so that as the latter is percussively acuated, it is at thesame time rotated. The piston striking bar 2 is provided withlongitudinal grooves 'I interlocked with straight lugs or vanes formedinternally within a sleevelike chuck nut 8 threaded at I0 within a chucksleeve I2 rotatably mounted within bores I3 and I4 formed in a frontchuck housing I5. yArranged within the bore I4 at the forward end of thechuck housing is a retaining ring l1 having a vreduced portion IBextending forwardly through an opening I9 at the forward end of thehousing. The chuck sleeve and the retaining ring are held againstrotation relative to each other when in their assembled position byinterlocking clutch jaws 2I and 22 formed at the forward and rearwardends of the chuck sleeve and retaining ring respectively. Openingthrough the forward -end of the retaining ring is a keyway 24 throughwhich the drill steel shank and lugs 25 formed on the shank may beinserted. Within the rearward portion of the retaining ring is anenlarged, circular bore 26 for receiving the lugs 25 after they havebeen moved rearwardly through the key opening 24. An annular radiallyextending shoulder 21 'is herein shown at the forward end of the bore26. The chuck sleeve has a longitudinally extending bore 28 of the samediameter as, and in alinement with, the bore 26. A driving bushing 30fits closely within the bore 28 and abuts against a shoulder 3I formedon the chuck sleeve when moved to its extreme rearward position.Extending through the driving bushing is a bore 32 for receiving therearward end of the drill st eel shank and for supporting the latter ina position to receive impact blows from the striking bar 2.

At the forward end of the driving bushing is a Y pair of diametricallyopposite projections 33 extending within the bore 26 of the retainingring, and these projections provide abutment surfaces 34 for engagementby the lugs on the drill steel shank When the drill steel is rotatedwithin the bore 26 to move theflugs out of alinement with the keyway24.* Desirably these projections abut, or substantially abut, theshoulder 21 when the parts are in assembled relation. Extendingrearwardly from the projections 33 are slots 35 formed in the drivingbushing for receiving the lugs on the drill steel shank when they havebeen moved into engagement with the abutment surfaces 34 and then movedrearwardly within the chuck. The slots are of such width that only aslight turning of the drill steel is permitted when the drill steel lugsare received in them and the drill is held against release from the keyopening i 24. The projections 33 on the driving bushing, extendingforwardly, engage the retaining ring at the forward end of the bore 26asr above described, and hold the driving bushing against the shoulder3| on thechuck sleeve when the chuck mechanism is assembled. The drivingbushing may be made to t the bore 28 in the chuck sleeve so closely thatnothing more will be needed to hold it against turning relative to thechuck sleeve, but to make sure that the driving bushing and chuck sleeveare assembled and held in their proper positions there is formed withinthe outer surface of the driving bushing a groove 31 that registers witha groove 38 formed withinrthe wall of the bore 28 in the chuck sleeveand forms an opening for a suitable locking pin 39. t

Theprojections 33 on the driving bushing are shown as being of suchlength that there is provided :between the forward end of the bore 26 inthe retaining ring and the forward faces 40 of the driving bushing atthe base of the projections 33 a space that is of but slightly greaterlength than the lugs on the drill steel shank. As the drill steel lugsare moved through the key opening 24 they enter the bore 26 and arepermitted to move rearwardly, before engaging the surfaces 40, only farenough to bring them completely within the bore so the drill steelcan-be rotated to bring the lugs against he abutment surfaces 34 on theprojections 33. After the lugs have been moved against the abutments 34they are in position to be received by the` slots and the drill steelcan be moved rearwardly in the chuck to a position for receiving theblows from the striking bar. The space within which the drill steel may.be rotated may of course be varied in length, but to reduce the chancesof an inadvertent release of the drill it is desirable to hold thelength to a minimum. The driving bushing may be noted to comprise arearward annular portion 4l having forwardly projecting mutuallyopposite portions 42 spaced from each other by the slots 35, these slotsproviding driving surfaces 43 to engage and drive the steel lugs and theportions 42 terminate, except for their projections 33, in conicalsurfaces as above noted, which limit the initial inserting movement ofthe steel.

As a result of this invention it will be noted that an improved chuckmechanism has been provided wherein the drill steel is positively lockedwithin the chuck during operation of the drill. It will further be notedthat the drill steel is prevented from moving appreciably within thechuck mechanism during operationfof the drill and the wearing of theparts is reduced. The mechanism is of -rugged construction and may beeasily assembled. The driving bushing has portions of the *t will beclearly apparent to those skilled in the art.

While there is in this application specifically described one form whichthe invention may assume in practice, it will be understood that thisform of the same is shown for purposes of illustration and that theinvention may be modified and embodied in various other forms withoutdeparting from its spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In a rock drill chuck mechanism for use with a lugged drill steel, incombination, a rotating chuck sleeve, a member rotatable with said chucksleeve and having an opening for receiving the shankfand lugs of a drillsteel, a recess within said member for receiving the drill steel lugsand within which said lugs are movable relative to said opening uponrotation of said drill steel, a driver member fory receiving anddrivingthe shank of said drill steel and rotatable with said chucksleeve, projectiong portions formed on said driver member and providingabutment surfaces against which said lugs abut on predetermined movementof said lugs in said recess, and grooves in said driver member forreceiving said lugs and holding said drill steel against rotationrelative to said member.

2. In a rock drill chuck mechanism for use with a lugged drill steel,incombinatiomarotating chuck sleeve, a member rotatable with said chucksleeve and having an opening for receiving the shank and lugs of a drillsteel, a recess within said member, circular in cross section, forreceiving the drill steel'lugs and Within which said lugs are movablekrelative to said opening upon rotation of said drill steel, a drivermember arranged within said chuck sleeve for receiving and driving theshank of said drill steel and rotatable with said chuck sleeve, andgrooves in said driver member for receiving said lugs on predeterminedangular movement of the latter in said recess and locking said drillsteel against rotation relative to said member.

v,3. In a rock `drill chuck mechanism for use with a lagged drill steel,in combination, a rotating chuck sleeve, `a member rotatable with saidchuck sleeve and having an opening for receiving the shank and lugs of adrill steel, a recess within said member, circular in cross section, forreceiving the drill steel lugs and within which said lugs are movablerelative to said opening upon rotation of said drill steel, and a drivermember for receiving and driving the shank of said drill steel andrrotatable with said chuck sleeve, said driver member having groovestherein extending longitudinally thereof for receiving said lugs onpredetermined rotation of said drill steel and holding said drill steelIagainst rotation relative to said member and said driver member furtherhaving projections extending into said recess for guiding said lugs intosaid grooves.

4. In a chuck mechanism for supporting and rotating a lugged drillsteel, the combination comprising a rotating chuck sleeve, a memberrotating with said` chuck Sleeve and having an opening for receiving theshank and lugs of a drill steel,`

a recess within said member for receiving the shank and lugs of saiddrill steel and within which said lugs are movable angularly relative tosaid opening upon rotation of said drill steel, means providing surfacesfor limiting the angular movement of said lugs in said recess, and meansfor receiving said lugs and holding said drill steel against rotationrelative to said member in a position out of contact with said surfaces.

'5. In a chuck mechanism for supporting and rotating a lugged drillsteel, the combination comprising a rotating chuck sleeve, a memberrotating with said chuck sleeve and having an opening for receiving theshank and lugs of a drill steel, said member providing a chamber forreceiving the shank and lugs of said drill steel and within which saidlugs are movable relative to said opening upon rotation of said drillsteel, and means rotating with said chuck sleeve and providing groovesfor receiving said lugs and holding said drill steel against rotationrelative to said member and further providing abutments extending intosaid chamber for halting rotation of said steel with the lugs thereof inalinement with said grooves.

6. In a chuck mechanism for supportingand rotating a lugged drill steel,the combination comprising a rotating, chuck sleeve, a member rotatingwith said chuck sleeve and having an opening for receiving the shank andlugs of a drill steel, said member providing a chamber for receiving theshank and lugs of said drill steel and within which said lugs aremovable angularly relative to said opening upon rotation of said drillsteel, and means rotating with said chuck sleeve and providing a wallfor said chamber and also grooves for receiving said lugs after movementof the latter against said wall in said vchamber and holding said drillsteel against rotation relative to said member.

7. In combination, in a chuck mechanism for supporting and rotating alugged drill steel, a chuck sleeve and a locking ring connected forturning together and providing a circular recess to receive and permitturning of the lugs of a lugs are receivable for holding the latter inlocked` A position and providing surfaces which are adapted drivingly toengage such lugs, said spaced portions having forward projectionsproviding surfaces in alinement with the driving surfaces on saidportions for limiting the rotation of the lugs of the drill steel. 8. Incombination, in a chuck mechanism for supporting and rotating a luggeddrill steel, a chuck sleeve and a locking ring connected for turningtogether and providing a circular recess to receive and permit turningof the lugs of a drill steel into and out of locked position, and adriver member within said chuck sleeve having a bore for receiving theshank of the drill steel and spaced portions between which the drillsteel lugs are receivable for holding the latter in locked position andproviding surfaces which are adapted drivingly to engage such lugs, saidspaced portions having forward surfaces limiting the insertion of thelugs of the drill steel while the latter is in unlocked position, andsaid spaced 75 portions also having, extending forwardly beyondsaidforward surfaces, projections for limiting rotation of the drill steelwithin the circular recess and guiding the lugs of the drill steel forrearward movement between said spaced portions, said projectionsengageable at their forward ends with said locking ring 9. Incombination, in a chuck mechanism for supporting and rotating a luggeddrill steel, a rotating chuck sleeve, a member rotating with said chucksleeve and having an opening for receiving the shank and lugs of a drillsteel, said member providing a chamber for receiving the shank and lugsof said drill steel and within which said lugs are movable angularlyrelative to said opening into and out of locked position upon rotationof said drill steel, a driver member rotating with said chuck sleeve andhaving a bore providing a bearing surface for said drill steel shank,projecting portions formed on said driver member and extending into saidchamber for stopping angular movement of said lugs in locked position,and notches in said driver member extending rearwardly from saidprojecting portions and having substantially the same transversedimensions as said lugs for receiving the latter and holding them inlocked position.

l0. In a chuck mechanism for supporting and rotating a lugged drillsteel, the combination comprising a rotating chuck sleeve, a memberrotating with said chuck sleeve and having an opening for receiving theshank and lugs of a drill steel, a recess formed in said member forreceiving the lugs of said drill steel and within which said lugs aremovable angularly relative to said opening into and out of a lockingposition upon rotation of said drill steel, abutment means for stoppingthe angular movement of said lugs in said recess in said lockingposition, and a driver member rotating with said chuck sleeve and havinggrooves extending rearwardly from said abutment means for receiving saidlugs when moved to said locking position andl holding said drill steelagainst rotation relative to said first mentioned member.

1l. In combination, in a chuck mechanism for supporting and rotating alugged drill steel, a chuck sleeve and a locking ring connected forVturning together, an opening extending through said locking ring forreceiving the shank and lugs of a drill steel, a recess in said lockingring for receiving the lugs of said drill steel and within which saidlugs are movable angularly relative to said opening into and out of alocking position upon rotation of said drill steel, a driver memberWithin said chuck sleeve and having forward surfaces limiting theinsertion of the drill steel lugs Within said recess, projectingportions on said driver member` limiting the angular movement of thelugs of said drill steel within said recess to a locking position, andspaces in -said driver member of substantially the same transversedimensions as said lugs for receiving the latter after being moved tolocking position and holding y,the same against angular movement,

12. In a drill steel chuck mechanism, a rotatable driver member havingparallel projections, a locking member connected to said driver memberfor rotation therewith and having a front key opening and a circularrecess, the lugs of a drill steel shank being insertable through saidkey opening into said recess and the steel being turnable to move saidlugs laterally in said recess to' bring the lugs out of registry withthe key opening, and said projections on said driver member extendingforwardly into said circular recesszandI providing stop surfacesfor thelugs for limiting turning of the steel when the latter is locked in thechuck mechanism. v;

13. In a drill steel chuck mechanism, a rotatable driver member havingparallel projections, a locking member connected to said driver membervfor rotation therewith and having a front key opening and a circularrecess, the lugs of a drill steel shank being insertable through saidkey opening into said recess and the steel being turnable to move saidlugs laterally in said recess to bring the lugs out of registry with thekey oepning, said projections on said driver member extending forwardlyinto said circular recess and providing stop surfaces for the lugs forlimiting turning of the steel when the latter is looked in the chuckmechanism, and said driver member having an opening for receiving thesteel shank and having abutment surfaces located rearwardly of saidprojections and engageable with the steel' lugs for rotating the steelwith said driver member.

14. In a drill steel chuck mechanism, a chuck housing, a driver memberrotatable within said housing and having a central bore for receivingthe shank of a drill steel and lateral grooves for receiving the lugs onthe steel shank, said grooves preventing substantial rotation of thesteel in either direction with respect to the driver member whilepermitting longitudinal reciprocation of the steel, a looking memberrotatable within said housing and having a front key opening and arearward circular bore, the steel lugs Abeing insertable through saidkey opening into said circular bore and said steel lugs being rotatablein -the circular bore to move out of registry with said key opening tolock the steel in the chuck mechanism, said locking member beingconnecte-d to said driver member for rotation therewith, and said drivermember having parallel projections extending forwardly into saidcircular bore in said locking member, said projections providing stopsfor the steel lugs with which the latter are engageable for locating thelugs in registry with said grooves when the steel is in locked positionin the chuck mechanism, said steel shank when saidl lugs are inengagement with said projections being movable rearwardly into the boreof said driver member and said grooves receiving the steel lugs as thesteel is moved rearwardly.

15. In a chuck mechanism for supporting, rotating and retaining a luggeddrill steel, the combination comprising a chuck housing having a borefor rotatably receiving steel supporting and rotating and steelretaining devices, ar retainer member rotatably supported in said boreand having intercommunicating openings for receiving the shank and lugsof a drill steel and rearwardly of said openings a circular recess inwhich the lugs ofthe steel are rotatable out of alinement with the firstmentioned openings for receiving them, and means forminga chuckrotatably received in said bore rearwardly of said retainer member andproviding surfaces for limiting the angular movements of the lugs in`said recess and slots for receiving said lugs and hold'- ing. saiddrill steel against substantial rotation in either direction relativetosaid chuck-forming,

means.

16. In a chuck mechanism for supporting, ro-` tating and retaining alugged drill'steek the` cornbination comprising a chuck housing havingalbore for rotatably receivingY steel supporting` andi rotating and steelretaining devices,y a retainer member rotatably supported in said boreand having interoommunicating openings for receiving the shank and lugsof a drill steel and rearwardly of said openings a circular recess inwhich the lugs ofthe steel are rotatable out of alinement tvith thefirst mentioned openings for receiving them,l and means forming a chuckrotatably supportedin said bore rearwardly of said retainer member andproviding surfaces for limiting rec- *tilinear movement of said lugsinwardly after .they pass through the rst mentioned openings Iing theshank and lugs of a drill steel and rearwardly of said openings acircular recess in which the lugs of the steel are rotatable out ofalinement with the first mentioned openings for receiving them, andmeans forming a chuck rotatably supported in said bore rearwardly ofsaid retainer member and having portions projecting forwardly into saidcircular recess for limiting turning of said lugs about the-axis of thesteel and providing surfaces for limiting the angular movements of thelugs in said recess and slots for receiving said lugs and holding saiddrill steel against substantial rotation in either direction` relativeto said chuck-forming means.

18. In a chuck mechanism for supporting, rotating and retaining a luggeddrill steel, the combination comprising a rotatable chuck sleeve, adriver member having a bore for receiving a drill steel shank, saiddriver member further'having grooves for receiving the lugs of a drillsteel and also having forwardly projecting portions certain sides ofwhich are in alinement with certain walls of said grooves and the Iothersides of which are angularly spaced from the opposite walls of saidgrooves, said driver member having transverse surfaces extending betweensaidv last mentionedV surfaces and said grooves, and a locking memberhaving communicating shank and lug receiving openings through which thesteel shank and lugs-may be passed and a circular recess communicatingwith said openings in which said lugs are rotatable, said4 projectingportions extending tinto said recess for limiting the turning of thelugs therein and saidtransverse surfaces limiting inward movement ofsaid lugs-in said recess, and said driver member andv said chuck sleevefixed against relative rotation and said chuck sleevev andA said lockingmember connected together with.V said grooves-out of alinement with thelug receiving openings in said locking member.

19. In a drill steel chuck mechanism, a rotatabley driver member havingparallel forwardly extending projections, a locking member connected tosaid driver member for rotation therewith` and havinga front key openingand a rearwardly disposed circular recess, said key opening being.formed to permit the passage of the lugs of a drill steel shanktherethrough and said recess being of an internal diameter to permitfree turning movement lbetween saidV lugs and said locking member, Saidprojections on said driver member extending forwardly into said circularrecess and providing stop surfaces to cooperate with the lugs forlimiting relative turning movement between the steel and said lockingmember, and said driver member further providing openings for receivingthe lugs and holding the drill steel against substantial rotation ineither direction relative to said driver member, said last mentionedopenings bounded at their rearward sides, in terms of driver memberrotation, by surfaces of which said stop surfaces constitute forwardextensions.

20. In a chuck mechanism for supporting, rotating .and retaining alugged drill steel, the combination comprising a chuck housing having abore, a retainer member rotatably supported in said bore and havingintercommunicating openings ior receiving the shank and lugs of a drillsteel and, rearwardly of said openings, a circular recess of a diametersuch as to receive the lugged portion of a steel and permit freerelative rotation between such portion and said retainer member, andmeans forming a chuck also rotatably supported in said bore and disposedrearwardly of said retainer member and providing surfaces for limitingrectilinear movement of the lugs inwardly after they pass through thefirst mentioned openings for receiving them, and further providing abore and diametrically oppositely disposed recesses communicating withsaid bore, said bore and said last mentioned recesses adaptedrespectively to receive the shank portion and the lugs of a drill steel,and said chuck forming means still further providing surfaces extendingforwardly substantially to the forward end of said circular recess, saidsecond mentioned recesses receiving the lugs during drilling and holdingthe drill steel against substantial rotation in either directionrelative to the chuck forming means, and said surfaces constitutingforward extensions of the rearward sides of said last mentioned recesseswhereby, Whether during drilling or during removal of the steel from ahole, the lugs of the steel may be driven over the major portion of therearwardly facing sides thereof.

21. In a drill steel chuck mechanism, a rotatable driver member, alocking member connected to said driver member for rotation therewithand having a front key opening, one of said members having a circularrecess and the other member having parallel projections extending intosaid recess, said key opening being formed to permit the passage of thelugs of a drill steel shank therethrough, 'and said recess being of aninternal diameter to permit free turning movement between the lugs andsaid locking member, said projections extending into the circular recessand providing stop surfaces to cooperate with the lugs for limitingrelative turning movement between the steel and said members, and saiddriver member providing openings for receiving the lugs of the drillsteel and holding the same against substantial rotation in eitherdirection relative to the driver member, said last mentioned openingsbounded at their rearward sides, in terms of driver member rotation, bysurfaces substantially coplanar with said stop surfaces on saidprojections.

22. In a drill steel chuck mechanism, a chuck housing having a bore, arotatable driver member in said bore, a separate locking member in saidlbore, said locking member connected to said driver member for rotationtherewith and having a front key opening, said driver member and saidlocking member cooperating to provide the boundaries of a recess of'such size and oo nformation as to permit turning movement between thelugs of a lugged drill steel and said locking member, and said keyopening being formed to permit the passage of a lugged drill steel shanktherethrough and into said recess, and one of said members havingprojections thereon extending into said recess and providing stopsurfaces to cooperate with the lugs of a drill steel for limitingrelative turning movement between the steel and said members, and saiddriver member providing openings for receiving the lugs of a drill steeland holding the same against substantial rotation in either directionrelative to the driver member, said last mentioned openings bounded attheir rearward sides, in terms of driver member rotation, by surfaceswhose longitudinally extending elements are substantially in alinementwith longitudinally extending elements of said stop surfaces.

23. In a drill steel chuck mechanism, a chuck housing having a. bore, arotatable driver mem.- ber in said bore, a locking member also in saidbore and detachably connected to said driver memb-er for rotationtherewith and having al front key opening, said key opening being formedto permit the [passage of the lugs of a lugged drill steel shanktherethrough, and said members cooperating to bound an internal chamberhaving portions in which said lugs are turnable relative to said membersand having longitudinally extending, substantially diametricallyoppositely disposed walls :for limiting the relative movement betweensaid lugs and said members and halting the relative turning movement ina position in which said lugs are angularly displaced with respect tosaid key opening, said driver member formed to provide substantiallydiametrically oppositely disposed openings for Vreceiving the lugs whenthe same have passed rearwardly beyond said chamber and to maintain saidlugs against substantial rotation in either direction relative to saiddriver member when in said openings, said openings last mentioned havingat their rearward sides, in terms of driver member rotation, walls eachof Which lies in substantially the same surface with one of said firstmentioned walls.

24. In a chuck mechanism for supporting, rotating and retaining a luggeddrill steel, the combination comprising a chuck housing having a borefor rotatably receiving steell supporting and rotating 4and steelretaining devices, a retaining member rotatably supported in said boreand having intercommunicating openings for receiving the shank and lugsof a drill steel, the drill steel and said retaining member beingrelatively rotatable to effect a positioning of the parts in which thesteel lugs are out of registry with said lug receiving openings, to lockthe steel in the chuck mechanism, and means forming a chuck rotatablyreceived in said bore rearwardly of said retainer member and to whichthe latter is detachably connected and which is held against rotationrelative to said retainer member and which provides surfaces forlimiting the angular movements of the lugs` when the latter are inlocked position with respect to said retainer member, and longitudinalrecesses for receiving said Vlugs and holding the steel againstsubstantial rotaticn in either direction relative to said chuck formingmeans.

JOHN C. CURTIS.

